This invention relates to a subsea well housing installed at the ocean floor, a casing hanger connectable to the upper end of a casing string and supported in the bore of the housing to suspend the casing string in the well bore, and a tubing hanger connectable to the upper end of a tubular string and also supported within the housing bore for suspending the tubular string within the casing string and use of a ball valve for hydraulically controlling flow in a first embodiment, through passageway means in the tubing hanger which connects the annulus between the casing and tubular strings and the bore of the housing above the tubing hanger, and in a second embodiment, in the bore below the tubing hanger.
During the completion of an offshore well, the casing and tubing hangers are typically lowered into supported positions within the wellhead housing through a blowout preventer (BOP) stack installed above the housing. Then, following completion of the well, the BOP stack is replaced by a Christmas tree having suitable valves for controlling the production of well fluids.
In most versions of the tree assembly, the casing hanger is sealed off with respect to the housing bore and the tubing hanger with respect to the casing hanger or the housing bore, so that the tubing effectively forms a fluid barrier between the annulus, that is between the casing and tubular strings, and the bore of the housing above the tubing hanger. However, during completion of the well, as well as after completion of the well, there may be reasons to communicate between the annulus and housing bore and thus permit fluid circulation between them. The present invention relates to a tubing hanger with passageways connecting them and shutoff mechanisms for controlling flow through the passageways so that the passageways may be opened or closed and well fluid contained at least during those intervals in which the BOP stack or Christmas tree is removed.
Subsea tubing hangers having shutoff mechanisms of this general type are shown, for example, in U.S. Pat. Nos. 3,360,048, 4,335,526 and 4,449,583 as well as in U.S. Pat. Nos. 5687794, 5143158, 5044432 and 4333526. In most of the patents, however, as well as in other apparatus of this type, the passageways through the tubing hangers are typically controlled by a shutoff mechanism or a valve which has sealing parts of elastomeric material which may be damaged by extreme heat or other deleterious conditions of the well fluids.
Also, in the valves of certain of these patents, movement of the shutoff mechanism from closed to open positions requires the installation and manipulation of a separate tool which is cumbersome and subject to breaking and not hydraulic manipulation. Furthermore, in most situations, the shutoff mechanism is moved from closed to open positions by springs, which are highly susceptible to malfunction.
None of the shutoff mechanisms disclosed focus on the safety aspects of controlling fluid flow through use of a ball safety valve.
An object of this invention is to provide a safety valve, and in particular either a ball valve in a tubing hanger or disposed in a separate member below the tubing hanger body, which is hydraulically operable for controlling the passageway to minimize the possibility of leakage past the fluid barrier provided by the hanger.
An object of the invention is to provide a safety valve, which is so reliable and inexpensive to install, that the valve assembly has significant environmental advantages, and lower construction costs.
A further object of the invention is to provide a ball valve either integral within the tubing hanger or disposed in a separate member below the lower end of the tubing hanger body, which can be operated in a reliable manner, without requiring a single additional tool.
The present invention comprises an apparatus for use in a subsea well including a housing having a bore, wherein the apparatus comprises: a tubing hanger having an upper end and a lower end including a tubing hanger body having an annulus therethrough, connectable to the upper end of the tubing hanger on an tubular string which is adapted to be supported in the bore of the housing so as to suspend the tubular string therein; a ball valve disposed in the annulus, adapted for opening and closing the annulus, comprising a ball valve body disposed within a valve chamber in the tubing hanger body which forms a continuation of the first section of the tubing hanger passageway at one end and which is closed at its opposite end; a tubular valve housing for the ball valve; the ball valve body having a ball valve closure member substantially in the form of a spherical ball defining two annular valve seats concentric with the annulus for the ball valve; the spherical ball being longitudinally movable and rotatable extending transversely in alternating positions between spherical upstream valve seat and spherical downstream valve seat thereby preventing flow through the flow passage; and means responsive to pressurized fluid from a remote source for hydraulically moving the spherical ball from an open to a closed position and from a closed position to an open position.
Optionally, in another embodiment of the invention, the ball valve may be disposed in a separate member below the lower end of the tubing hanger body.